Galvanizing waste-derived Zn-induced defective Fe-based metal-organic frameworks as superior adsorbents for enhanced...

The derivation of defect-engineered metal-organic frameworks (MOFs) from industrial waste simultaneously mitigates environmental pollution, reduces MOF synthesis costs, and enhances adsorption performance. Herein, this study demonstrates a sustainable strategy for the resourceful synthesis of an iron-based MOF, s-MIL-100(Fe), using galvanizing pickling waste liquor (80.5 wt% Fe²⁺, 18.8 wt% Zn²⁺) as metal precursors. Although zinc ions do not incorporate into MOF frameworks, their coexistence induced the generation of coordinatively unsaturated metal sites (CUMS), enabling s-MIL-100(Fe) to achieve an ultra-high adsorption capacity of 721 mg g^-1 for doxycycline (DOX) at 303.15 K. In addition, Zn-mediated defect engineering increased the porosity of s-MIL-100(Fe), yielding optimized textural parameters (specific surface area: 733.4 m² g^-1; pore volume: 0.74 cm³ g^-1), and outperformed commercial c-MIL-100(Fe) by 48.4 % in adsorption capacity with a shorter equilibrium time. Furthermore, s-MIL-100(Fe) exhibited robustness across a pH range of 2-10, in multi-ion matrices and under humic acid interference, while retaining 90 % capacity over four regeneration cycles. Synergistic mechanisms involve CUMS-driven coordination, π-π stacking, and pore confinement, supplemented by hydrogen bonding and electrostatic interactions. By transforming hazardous metallurgical waste into high-performance adsorbents, this work offers a sustainable approach that simultaneously addresses industrial waste management and advanced material synthesis. Notably, s-MIL-100(Fe) demonstrates >97 % DOX removal efficiency in real contaminated waters, including aquaculture effluents, municipal wastewater, and river systems, validating its practical utility in environmental remediation. The Zn-assisted defect modulation strategy provides new insights into the structure-property optimization of waste-derived MOFs, highlighting the untapped potential of impurity ions in functional material synthesis.